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Vapor lock/boiling gas

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So I raced a local hare scramble today in sunny 80 degree weather and couldn't finish the race because of what I think is vapor lock and or boiling gas issues. It's a 08 yz 250f, I ran about 17 miles perfectly, not running the bike too hard and not over revving it a lot, never stalled or fell even once so the bike was running and moving the entire time, then all the sudden it was like a plug fouling and would just randomly cut out until finally it would barely run. I pulled over checked the choke and gas, both good, then opened the gas cap and it was like a blowout on a tractor trailer, pressure hit me in the face with a huge wiff of gas and it was half full n bubbling in my tank. Once home I checked and the coolant, which is engine ice, was completely full. How do I prevent this from happening and what is going on?

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Not sure.. Maybe check your vent on the gas cap? Could be plugged and not allowing it to vent. So its building pressure in the tank.

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Yeah I'm going to put just a straight vent hose in it with no check valve or anything so it can vent better, but my gas shouldn't get that hot anyway right?

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Im just wondering if its not really the heat causing it rather than just building pressure from not venting like its supposed to. My dads grizzly 700 does it pretty often, same kind of thing blows a bunch of pressure out when you open the gas cap. His has never quit on him because of it though.

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If you were using one of those stubby gas cap vents with the valve in it, those things are notorious for causing such issues. I guess there's a good reason they don't come stock on a bike. Good move going back to a straight piece of vent line.

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If you were using one of those stubby gas cap vents with the valve in it, those things are notorious for causing such issues. I guess there's a good reason they don't come stock on a bike. Good move going back to a straight piece of vent line.

No i was running the stock vent but it has the one way valve/check ball In it which is completely gone as far as I'm concerned now. We will see this weekend when I go riding again, it's supposed To get close to 80 again and I'm just going to run a straight vent hose now

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